Fluid catalytic cracking (FCC) processes convert relatively high boiling or heavy hydrocarbon fractions, such as crude oil, straight-run atmospheric gas oils, vacuum gas oils, certain atmospheric residues and heavy stocks recovered from other refinery operations, into more valuable lighter hydrocarbons, such as those in the gasoline boiling range. In a typical FCC process, a high boiling feedstock is contacted in one or more reaction zones with a particulate cracking catalyst. The reaction zones are maintained at conditions suitable for carrying out the desired cracking reactions and are free of hydrogen.
The absence of hydrogen in FCC reaction zones results in the formation of a cracked product stream with a significant quantity of aromatic and other unsaturated compounds that may be favorably blended into gasoline due to their high octane values. These gasoline boiling range hydrocarbons are normally removed as a vapor fraction from an FCC fractionation column that separates the FCC reactor effluent after exiting the reaction zone(s).
Recently, the operation of many FCC processes has focused on raising yields of light olefins, and propylene in particular, by increasing the extent of cracking or conversion. Propylene is an important raw material in many petrochemicals, and its production from sources other than FCC, such as its production as a byproduct of steam cracking, is not expected to meet the increasing demand. Typically, FCC processes operated at conditions promoting the formation of propylene also form a nearly equal amount of butenes. Conventionally, the butene produced by the FCC process is used in the production of alkylates.
Typically, the heavy naphtha produced in the FCC unit is charged to a reforming unit to produce aromatics. When operated at high severity to maximize propylene production, conventional integrated refinery and petrochemical complexes have a limited ability to manage the quantity and type of feed molecules that readily convert to aromatics during reforming.
Accordingly, it is desirable to provide methods and apparatuses for processing hydrocarbons that convert olefins to longer chain normal paraffins that may be processed to form aromatics. It is also desirable to provide methods and apparatuses for processing hydrocarbons that enable an increase in the production of aromatics from products of the FCC process. Also, it is desirable to provide such methods and apparatuses that operate economically. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.